Many thanks for thoughts and info folks, much appreciated. Seems most convincing to say the pigs foot is being made in the forge, not a tool being used there, (not heated anyway.)
Fiddle tune names don't often make much sense, they're just a tag like a racehorse name, but this one's more obscure than most. Why did someone think, "I'll call that tune, 'Shove the pigs foot a little further in the fire.' !"
Cheers,
Tom